Patent GB-1462289-A (GB)
Title: Automatic power transmission for an automotive vehicle
IPC: B60W10/10
Filed: 1974-08-05
Abstract: 1462289 Change-speed control NISSAN MOTOR CO Ltd 5 Aug 1974 [17 Aug 1973] 34355/74 Heading F2D The invention is based on what is shown in Specification 1,444,641, the following abridgment only defining the invention claimed and any difference in subject-matter. The changespeed gear itself and the fluid control circuit are the same as those in the earlier Specification, the drawings being identical (although using different reference numerals), and reference should be made to the abridgment of the earlier Specification for details and the functions of both these items, which are all repeated in this Specification. The invention claimed here (and also described in the earlier Specification) is directed to the maintaining by the main pressure regulator valve (90 here, 104 in the earlier Specification) of a first level a, Fig. 2, of line pressure 122 which is responsive to throttle pressure 242 in all forward drives; a second level, b, higher than the first and also responsive to throttle pressure but at a steeper rate, in reverse drive, for pressure augmentation ; and a third level lower than the first level, as indicated by the part of the line b near zero throttle, and also responsive to throttle pressure, during idling in reverse. This ensures a soft entry into and a soft start in reverse. For this purpose the pressure regulator valve 90, Figs. 4a and 4c, has four loading ports as follows. A first port 250, for pressure decrease, constantly receiving line pressure 122 from the pump 80; a second port 262, for pressure increase, receiving line pressure 150 in forward drive settings only (from the forward clutch line 150); a third port 260, for line pressure increase, receiving throttle pressure 242; and a fourth port 254, which, for pressure decrease, receives in all forward drives line pressure from the forward clutch line 150, through a shuttle valve 294, which, in all other settings, with the line 150 exhausted, is substituted by pressure in a line 298, which is supplied with hysteresis pressure (which is a constant pressure lower than line pressure) from the hysteresis valve (92 here, 128 in the earlier Specification),through the idling valve 96 (122 in the earlier Specification), only when that valve 96 is opened by the absence of throttle pressure during idling. In addition the pressure regulator 90 establishes a fourth level of line pressure in manual ratio settings 1, 2 and 3, by a throttle back-up valve 88 (138 in the earlier Specification), which causes a pressure slightly lower or approximately equal to line pressure 122 to be substituted for throttle pressure 180 in the line 242 feeding the regulator port 260, whereby line pressure is augmented and rendered independent of throttle pressure. The present Specification includes two main circuit modifications which are not present in the earlier Specification. In Fig. 5, not shown, the idle valve 96 is not used to obtain pressure reduction on reverse idle. The solenoid valve (94 here, 120 in the earlier Specification) is replaced by a valve (650) which is directly actuated by the plunger (678) of a solenoid (676) energized by a single switch closed only by accelerator release, to supply hysteresis pressure (320 here, 328 in the earlier Specification) directly to the line 298 and, in all but forward drive settings, through the shuttle valve 294 (130 in the earlier Specification) to the main pressure regulator 90 (104 in the earlier Specification), thereby achieving reduction in line pressure on reverse idle as before. In Fig. 6, not shown, such a valve (682) is used with the idle valve (96) but its solenoid is energized on accelerator kickdown as well as release through switches (708, 710), the release causing reduction in line pressure as above in all except forward drive settings.